Lactobacilli fortis in that Nestle drink, Chamyto. And Lactobacilli shirota strain in that japanese skim milk drink, Yakult. Like, I got sick once, with cough and colds and another time with pharyngitis. And I was wondering, when I was drinking those antibiotics, did it also kill the "good" bacteria that I drank? I drink Yakult, not Chamyto, by the way.

And what's he difference between Lactobacilli shirota strain and Lactobacilli fortis?

Yes many antibiotics that are prescribed for infections will also destroy the "good" bacteria in the gut. That is why many antibiotics cause diarrhoea as a side-effect and why eating live yoghurt during and after a course of antibiotics will reduce  the severity of the diarrhoea.